The present invention relates to an apparatus for generating parallel light and, more particularly, to a parallel light generating apparatus which uses two arrayed mirrors.
In general, light may travel either omnidirectionally as from a point source, or as parallel (collimated) light. In the case of point source light, the light intensity (illumination) dissipates exponentially with respect to the distance travelled. On the other hand, parallel light can theoretically maintain its original energy level indefinitely, no matter how far it travels from the source. Therefore, parallel light is desirable for use in optical systems since it exhibits a constantlevel intensity throughout the proceeding path.
Meanwhile, an apparatus for generating a parallel beam of light from a light source generally uses a parabolic mirror to reflect rays emitted from the light source, which proceed as parallel light. In this case however, strictly speaking, there is a small non-parallel light component included in the parallel beam; namely, the rays which emanate directly from the light source proceed in a dispersed manner (represented by the dotted line in FIG. 1). Nevertheless, when parallel light including the nonparallel component travels a certain distance before being manipulated in some way, e.g., is concentrated or dispersed by a lens or other device, there are few problems contributable to the non-uniformity of the light intensity because the quantity of non-parallel light, having been sufficiently dissipated, is negligible.
However, in many optical instruments, a focusing lens is located very close to the lamp (light source), due to the size of the instrument itself. In such a case, the parallel light travels only a short distance before being manipulated, so that the non-parallel light component is still present at a relatively high level and thus acts like an effective component which, due to its non-uniform level, adversely influences the operation of the optical system. If the optical instrument is a projector, the included non-parallel component is projected onto the screen, imparting undesirably shaded areas.